Current Research

The Moon's impact basins and their deposits contain information about the timing, flux and composition of late accretion in the inner solar system. However, it is difficult to reliably determine the isotopic ages of particular basins because reheating by later impacts has affected chronometers to variable extent and gardening of impact ejecta has added complexity. Due to the robustness of zirconium minerals in lunar impactites, their isotopic ages can provide clues to the early lunar bombardment history, as they are more resistant to resetting than, for instance, K-Ar ages. For the present study we obtained U-Pb age distributions of zircons and baddeleyites from highland rock clasts in ancient Apollo 16 & 17 regolith breccias. Coupled with petrographic, geological and geochemical studies, reliable impact breccia ages can be linked to specific lunar basins by combining the data with advanced models of ejecta distribution and absolute model ages obtained by improved crater counting data to constrain the early lunar mass flux history.